Numerous items such as smart phones, smart watches, tablets, automobiles, aerial drones, appliances, aircraft, exercise aids, and game controllers may utilize motion sensors during their operation. In many applications, various types of motion sensors such as accelerometers and gyroscopes may be analyzed independently or together in order to determine varied information for particular applications. For example, gyroscopes and accelerometers may be used in gaming applications (e.g., smart phones or game controllers) to capture complex movements by a user, drones and other aircraft may determine orientation based on gyroscope measurements (e.g., roll, pitch, and yaw), and vehicles may utilize measurements for determining direction (e.g., for dead reckoning) and safety (e.g., to recognizing skid or roll-over conditions).
Motion sensors such as accelerometers and gyroscopes may be manufactured as microelectromechanical (MEMS) sensors that are fabricated using semiconductor manufacturing techniques. A MEMS sensor may include movable proof masses that can respond to forces such as linear acceleration (e.g., for MEMS accelerometers), angular velocity (e.g., for MEMS gyroscopes), magnetic field and many others. The operation of these forces on the movable proof masses may be measured based on the movement of the proof masses in response to the forces. In some implementations, the proof mass movement is converted to an electrical signal by capacitive sense electrodes.
In a typical MEMS sensor, the proof masses may be located in close proximity to a number of fixed surfaces. Fixed electrodes, anchors, external frames may be located within the same device layer as the proof masses and adjacent to the proof masses. In the presence of undesired external forces, such as shocks, can cause the proof masses to contact the fixed surfaces causing wear or even catastrophic damage. Even smaller undesired external forces that do not cause the proof masses to contact the fixed surfaces may impact the motion of the proof mass and thus the resulting accuracy of the measured parameters.